Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
16 Cards in this Set
- Front
- Back
- 3rd side (hint)
|
What is LET?
|
Linear Energy Transfer, it is the energy transferred per unit of track length in keV/µm
it is an average as the number of ionizations in any segment can vary greatly |
|
|
|
Characteristics of low LET
|
sparsely ionizing radiations (photons, xrays, gamma)
travels long distance through tissue higher energy radiation |
|
|
|
Characteristics of high LET
|
densely ionizing radiations (alpha, N,P)
travels short distance through tissue lower energy radiation |
|
|
|
Oxygen effect has significant effect on ___ LET radiation and little or none on ____LET radiation.
|
Oxygen effect has significant effect on LOW LET radiation and little or none on HIGH LET radiation.
|
|
|
|
What is RBE?
|
Relative Biological Effectiveness
how is it measured? |
A dose of radiation is compared to a "benchmark" dose of 250 keV x-rays as a ratio: dose of 250 keV xrays/ dose of any radiaton = RBE
|
|
|
What is optimum LET and why?
|
RBE increases with LET to about 100 keV/micrometer because ionizations at this level are at 2nm which is the diameter of a DNA helix
what is the dosage called above this level? |
OVERKILL
|
|
|
Name the 5 factors effecting RBE?
|
1. radiation quality (LET)
2. Radiation dose 3. number of dose fractions 4. Dose rate 5. Biological system or endpoint |
|
|
|
What is the law of Bergonie and Tribondeau? which is one of the most important concepts in radiobiology
|
Ionizing radiation are most effective against cells that are:
1. actively mitotic 2. undifferentiated 3. divide rapidly 4. have a long dividing future |
|
|
|
What are the units for measuring absorbed radiation dose?
|
Rems and Sieverts, 100 rems = 1 Sieverts
|
|
|
|
For the purposes of radiation protection there is assigned a Radiation Weighting Factor or quality factor Q. state the factors for 4 levels of radiation
|
Alpha - 20
High energy protons - 10 Thermal neutrons - 2 Beta, gamma, X - 1 |
|
|
|
State the occupational dose limits for
1. Whole body 2. organ, skin, extremities 3. lens of the eye |
1. Whole body - 5 rem/yr
2. organ, skin, extremities - 50 rem/yr 3. lens of the eye - 15 rem/yr |
|
|
|
What does ALARA stand for?
|
As Low As Reasonably Achievable
What is the ALARA philosophy for occupational dose limits? |
10% of NRC limits
|
|
|
What is the enhancement ratio for radiosensitizers?
|
Dose in rads to kill 63% w/o sensitisizer/dose in rads with sensitizer = Enhancement ratio
Over what # indicates a substance has radiosensitive properties? |
1
|
|
|
What is the only radiosensitizer that we are really concerned with?
|
oxygen
|
|
|
|
What is the most effective radioprotector?
|
sulfhydryl compounds
what is the problem with using them? |
an effective level ingested is toxic to the body
|
|
|
What is the dose reduction factor?
|
dose to kill 63% with protector/dose to kill 63% w/o protector where a DRF greater than 1 indicates protective qualities
|
it has protective qualities
|
